Phytotechnology Biomass Systems
There is no doubt that the enhanced, controlled atmosphere culture of algae for Biomass Production and garden crops for food is the way each home could achieve near self-sufficiency. After separating oil (for liquid fuel energy) the remainder of the algae can be digested to produce methane and a rich organic sludge that can be feed to our garden plants and thereby grow healthy organic produce. As you have pointed out some of our biomass can be palletized and fed to fish and poultry that have a 1 to 1 conversion ratio and therefore are ideal for a self-sufficient urban food production design. (Again, fish are the only feed conversion that is being explored by the NASA - CELSS program).
Plants and fossilized (oil and natural gas) and/or bio-concentrated residues (manure) can be used to create nitrogen fertilizers. The N2 bond is so powerful and stable that only plants have developed the catalysts that can crack the molecule and form amino acids. Even to date there is no equivalent synthetic chemical process. Natural processes of bio-fixation by soil bacteria depend on lighting strikes and are extremely slow acting. Just as we depend on the higher plants for the essential amino acids, the higher plants depend on the micro-biological algae to synthesize the nitrogenous organic enzymes that are the building blocks of the plant kingdom.
It is a life-science focus that is needed to address these (already far exceeded and living on biological capital) limits to growth. If we want to get onto a sustainable path we must live on our solar energy income (transformed and converted in various ways) and we will have to use plants - especially the single cell, primitive plants to produce the organic nitrogen that is needed to sustain life. Fortunately, mass cell culture is not land dependent (no soils need be depleted by excessive exploitation) because they grow in water media (i.e. tank farms). It is very responsive to technology inputs and can reach high levels of yield with advance culture methods.
Some algae will be grown by methods that optimize energy fuel production - producing fat. Some algae culture would optimize protein synthesis. Always the hydrocarbons will be predominant and can be converted to methane and methanol as many of the list members have pointed out. The residue Ė the organic nitrogen - can be used as a food and feed supplement and contains all the nutrients (in prefect balance) for producing other food crops. The rate of production is so high that if we allocated the roof area of our buildings to the Phytotechnology growing systems, it would be possible for communities to become substantially self-sufficient in food, energy and water. These designs are no different in concept that those that would be appropriate for long term space habitats ("On earth, as it is in the heavens").
How much space is needed:
State-of-the-art high tech commercial greenhouses can produce many crop cycles per year compared to outdoor gardens - 2 to 3 tomato - 15 lettuce - for example. They use CO 2 enrichment only part of the year (winter season). The yield that is achieved is 30 to 40 pounds per square foot per year (2 to 4-lb. of dry weight) There is no weeding and no chemicals used in growing. The watering and feeding can be completely automated. Harvesting and planting is on going and takes just a few hours per week. A family of four will have a good food supply from a climate controlled Sola Roof garden of only 2000 square feet - i.e. the top floor & roof level of their home. Out door gardens or further enclosed gardens or courtyard space can enhance the concept. The Earthship concept has shown that small pond and marsh constructions in or around our homes can provide a closed cycle biological water treatment and use.
I would expect that the algae growing (within the transparent roof system) will be 2 to 3 times as productive - thus producing about 6 to 12-lbs. of dry weight. About half of this is oil that could be converted to a liquid Bio Fuels?. Another 40% could be digested into methane. About 1 pound of nutrient concentrate (water soluble sludge) will remain to be used as liquid fertilizer. If we accept these numbers for time being - then you have about 9 pounds per foot per year of biogas and Bio Fuels? output. There is a small energy input from water pumping requirements. Let's say the family home with 2000 square feet of roof area can make 9 tons of fuel or 1800 gallons roughly. That is a little less than one gallon per square foot per year output.
Perhaps working backwards we could get an upper limit to the possible productivity. Perhaps my expectation for the algae is too high. But the relative performance of the food crops that I have quoted can be counted on. In fact there are some higher plants that are very good candidates for a secondary biomass crop that is grown below the algae roof culture system.
Different localities will have higher or lower solar potential say from a minimum of 3Kw/M2/day to 8Kw/M2/day. The estimates above would assume at about 6Kw/M2/day - or, 2190Kw/M2/yr - or, letís say FT 2?/year - of which we could expect to convert possibly 20% or 40-Kw per square foot. This is about 140,000 Btu. That is very close to one gallon of Bio Fuel per square foot per year.
What do you think of these numbers? Are they interesting enough? Are there some Ph Ds? who could comment?